In April 2013, the Two Oceans Aquarium once again released Ragged-tooth sharks back into the ocean as part of its on-going shark conservation efforts.

Two sharks, a male and a female, were tagged and returned to the sea off Gordon's Bay with support from Gemini Marine. The sharks' release forms part of a continuous release programme which was initiated with the release of a shark named Maxine in 2004. Her release set in motion the Maxine, Science, Education and Awareness (M-Sea) Programme. This programme is an AfriOceans Conservation Alliance initiative sponsored by the Save Our Seas Foundation.

Ragged-tooth sharks go through about 30 000 teeth in a lifetime as they are able to lose and then replace their teeth. (Picture: Mariola Biela)

A juvenile Raggie is released in the NZG's Aquarium. (Picture: Mariola Biela)

Eight sharks have subsequently been released from the Two Oceans Aquarium since 2004.

Exchange programme

The male shark released this year was collected as a juvenile by the Two Oceans Aquarium off the Eastern Cape coast. In May 2011, the young shark was transferred by air from Cape Town to the National Zoo (NZG) in Pretoria, where he was displayed in the Aquarium.

"We have an exchange programme in place with the NZG whereby we loan them juvenile Raggies for two years to display in their marine exhibit. The system works well as the sharks have often already spent time in our Aquarium adjusting to their new environment and then they head north to act as ambassadors in Gauteng. At the end of the two years, the NZG returns the sharks to us for release back into the ocean," says Tinus Beukes, Operations Manager at Two Oceans Aquarium.

The female shark released this year, known as Kay, has been a resident in the I&J Predator Exhibit at the Two Oceans Aquarium since 2009. She was collected in February 2009 at Hamburg, East London. At that time she measured 149 cm in length (notch length) and weighed 51,4 kg.

Monitoring their movements

Both sharks were tagged with acoustic Vemco tags (active for 10 years) before their release so that their movements can be monitored should they pass one of the many receiver base stations positioned along the South African coast.

"The National Zoo, as an inland conservation facility, is proud to be associated with the concerted shark conservation efforts being undertaken with the Ragged-tooth sharks housed at its aquarium in conjunction with the Two Oceans Aquarium in Cape Town," says Craig Allenby, Marketing Manager of the National Zoo.

Ragged-tooth sharks are known as 'Grey nurse' sharks in Australia and 'Sand tigers' in America. They occur in the Atlantic, Indian and Western Pacific. Ragged-tooth shark populations have been seriously depleted in Australia due to over-fishing.

Healthy population

As far as we know, South Africa has one of the healthiest populations of Ragged-tooth sharks in the world and these sharks are quite common along the entire sub-tropical east and south Cape coasts. However, although these sharks occur in positive numbers, they require protection and effective conservation management.

Ragged-tooth sharks attain a maximum total length of about 3,2 m and a maximum age of about 30 years.

By Angeliné Schwan, Communications Officer, NZG

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